private void installNewPiece() {
next_piece_canvas.clear();
cur_piece = next_piece;
cur_piece.setPosition(3, -4);
if (cur_piece.canPaste()) {
next_piece = randomPiece();
next_piece.setPosition(0, 0);
next_piece.paste(next_piece_grid);
next_piece_canvas.repaint();
} else gameOver();
}
